1. Field of the Invention
The present invention relates to a plasma display panel (PDP). More particularly, the present invention relates to a PDP in which an electrode shorted segment has various configurations enabling its formation at a substantially uniform thickness.
2. Discussion of the Related Art
A PDP displays images through excitation of phosphors by plasma discharge. Specifically, an applied voltage between two electrodes in a discharge region of the PDP generates a plasma discharge between them. Ultraviolet rays generated during the plasma discharge excite phosphor layers to display images. The different types of PDPs include alternating current (AC) PDPs, direct current (DC) PDPs, and hybrid PDPs.
FIG. 5 shows a partial exploded perspective view of a conventional PDP 100. The conventional AC-PDP 100 includes a lower substrate 101 and an upper substrate 102 provided opposing one another with a predetermined gap therebetween. Address electrodes 103 are formed on a surface of the lower substrate 101 opposing the upper substrate 102. The address electrodes 103 are formed in a stripe pattern substantially along direction Y. A dielectric layer 105 is formed on the lower substrate 101 covering the address electrodes 103, and a plurality of barrier ribs 107 are formed on the dielectric layer 105. The barrier ribs 107 function to maintain the panel gap and prevent crosstalk between discharge cells. A phosphor layer 108 is formed between each adjacent pair of the barrier ribs 107 covering the dielectric layer 105 and side walls of the barrier ribs 107.
Formed on a surface of the upper substrate 102 opposing the lower substrate 101 are display electrodes 104. The display electrodes 104 are formed substantially along direction X, that is, substantially along a direction perpendicular to the address electrodes 103. The display electrodes 104 are formed such that a pair of the same is positioned over each of the discharge cells defined by the barrier ribs 107. A dielectric layer 106 and a protection layer 109 are formed on the upper substrate 102 covering the display electrodes 104.
In the conventional PDP with this configuration, each pair of the display electrodes 104 is comprised of a sustain electrode and a scanning electrode. A drive voltage is received from the address electrodes 103 and the scanning electrodes to thereby effect address discharge therebetween and form a wall charge on the dielectric layer 105. Sustain discharge is effected between the sustain electrodes and the scanning electrodes in the discharge cell selected by the address discharge by a signal that is alternatingly supplied to the sustain electrodes and the scanning electrodes.
Accordingly, a discharge gas filled in the discharge region where the discharge cells are formed is excited such that the discharge gas generates ultraviolet rays. Visible light is generated by the excitation of the phosphors of the phosphor layers by the ultraviolet rays, thereby resulting in the formation of images.
A silver (Ag) paste is typically used to form sustain electrodes and scanning electrodes, as well as address electrodes. A screen printing or photolithography process is typically used to form these electrodes since they may be formed at widths of 70 to 80 μm. Lift-off and thin film methods are other possible alternatives. However, these conventional methods for forming electrodes may not be suitable when manufacturing large screen PDPs. Therefore, an offset printing process method is being explored, which may be used to precisely and stably print electrodes.
FIG. 6 is a schematic sectional view showing sequential steps of the offset printing process.
The offset printing process generally involves the main steps of paste deposition and doctoring, step A, an off process, step B, and a set process, step C. Step A involves depositing a paste 23 on an intaglio 21 having a plurality of indented grooves. A doctor blade 22 is scraped along the intaglio 21 in a direction (a doctoring direction) to remove excess paste 23, leaving paste 23 in the indented grooves. Next, in step B, a blanket 24 (partially shown), which may be made of silicone rubber and cylindrical in shape, is used to remove the paste from the indented grooves of the intaglio 21. Finally, in step C, the blanket 24 and the paste 23 are pressed against a substrate 25 to transfer the paste 23 onto the substrate 25.
However, the offset printing process may have drawbacks. Although this process may effectively form small and narrow electrode portions, when forming large electrode portions, such as terminal electrodes, problems may be encountered during the doctoring process since that process may be best suited for forming long and narrow electrode sections that extend along the doctoring direction. Hence, large electrode portions formed by the offset printing process may not meet desired quality standards.
FIG. 7 and FIG. 8 show problems with the conventional offset printing process just described.
FIG. 7 is a partial perspective view showing an intaglio 21 with a paste 23 formed thereon following an offset printing process. A doctor blade (not shown) was run across the intaglio 21 in a doctoring direction, as indicated in FIG. 7, to remove excess portions of the previously deposited paste 23.
FIG. 8 is a schematic sectional view showing the sequential steps involved in the offset printing process when forming shorted segments of sustain electrodes. The views are taken along line I-I of FIG. 7.
In step A of FIG. 8, after depositing the paste 23 on the intaglio 21, the doctor blade 22 is used to remove the overflow paste. At the beginning of the doctoring process, the remaining paste 23 is substantially coplanar with an upper surface of the intaglio 21. However, as shown in step B, as the doctor blade 22 progresses along the doctoring direction, it may enter a region where it no longer contacts the intaglio's upper surface, and the doctor blade 22 may descend into the intaglio's indented groove. This situation may continue as the doctor blade 22 further progresses along the doctoring direction, as shown in step C. At the end of doctoring process, as shown in step D, a middle portion of the paste 23 may be concave.
When transferring the paste 23 with the concave middle portion onto a substrate using a blanket to form sustain electrode shorted segments, the shorted segments may not be uniformly thick. The end result is that discharge characteristics of the PDP may be adversely affected by the uneven thickness of the shorted segments.